1. Technical Field of the Invention
The present invention relates to a debug device using an on-chip debugging function, and more particularly to a debug device that can expand the break function using an external circuit.
2. Conventional Art
Japanese laid-open patent application HEI 2-186448 (Japanese patent HEI 5-50016) describes an integrated circuit equipped with a debugging environment that enables software debugging by storing a primitive debugger program that enables debugging of the user program of a microcomputer ASIC while communicating with an external host computer in a ROM provided on the microcomputer ASIC chip.
Japanese laid-open patent application HEI 4-77833 (Japanese patent KEI 7-27472) describes an integrated circuit equipped with a debugging environment that enables debugging of programs stored in a user ROM and RAM externally, by performing the communication through a host computer via a serial communication block between a control CPU and the control ROM and RAM.
Japanese laid-open patent application HEI 8-161191 describes an in-circuit emulator that can perform debugging even when a high-speed MPU is a target.
Japanese laid-open patent application HEI 8-179958 describes a microcomputer (controlling electronic device) that is capable of performing debugging without using an ICE by executing a program for debugging assembled in the microcomputer according to a command from a host computer.
Japanese laid-open patent application HEI 10-214201 describes a microcomputer in which a debug circuit equipped with various functions used at the time of program debugging is provided in the microcomputer, and a flash memory electrically capable of writing/erasing incorporated on the same chip can be used as an emulation memory.
A magazine Nikkei Electronics, Mar. 22, 1999 edition, at P215-P225, describes the following in its article entitled “On-Chip Debugging Starts Penetrating In Assembly Software Development”. Methods in developing software for embedded equipment internally equipped with microprocessors are changing. There are an increasing number of cases to employ an “on-chip debugging” method in which a microprocessor having a debugging exclusive command added in a command set and an exclusive debugger are combined for debugging software.
In the on-chip debugging, the break function is realized by using a break circuit or the like that is mounted on the chip. To realize the break function, a register to store break conditions, addresses for the CPU to access the break conditions set at the register, a comparator circuit to compare data and the like are needed. By providing a plurality of break circuit sets, a plurality of break points can be set. However, when a plurality of break circuit sets are provided, a circuit size (the number of gates) of the debug circuit section increases. There are instances that are not economically preferable to increase the circuit size more than required when realizing microcomputers or ASIC microcomputers. Accordingly, the break function (the number of break points that can be set) that can be used in the on-chip debugging is generally limited to several (2-8) points. In an actual debugging work, a map break function for detecting that the execution of a program extends to outside of an expected address range, data break functions under complex conditions and the like may be needed. In this respect, there has been a demand to expand a break function in a debugging device that uses an on-chip debugging function.
The present invention has been made to solve the problems described above. It is an object of the present invention to provide a debug device using an on-chip debugging function, in which the debug device uses an external circuit to expand a break function.